If you compare JRuby with MRI Ruby, the memory consumption is indeed higher in JRuby. I am no expert in JRuby but as far as I know, the problem with it is that

If you compare JRuby with MRI Ruby, the memory consumption is indeed higher in JRuby. I am no expert in JRuby but as far as I know, the problem with it is that it can not fully take advantage of threading and thus suffers from similar problems as the MRI + some additional memory overhead. A Java web application however needs very little additional memory per request-handling thread, which makes its memory footprint much smaller when many parallel requests are involved. 100 ms for the home page in my Java app might not be great but, considering that 7 separate queries to the database are involved and that it runs on a very weak server, I think it is quite decent. And because of the use of concurrency (threading) there is a good chance that 100 ms for a single request translates into more than 10 requests per second. But I still wouldn't call my webapp lightning fast. I was calling java lighning fast because in my case I still get decent response times on bad hardware and with an inefficiently programmed application (7 db requests that could as well be cached and only refreshed every hour or so). You are absolutely right about the rails app however. The 1 second response time is not normal. I just measured again and suddenly I get similar response times as for the java app. The server must have been under heavy load before (maybe the automatic backup). I admit that my quick measurements are not very representative and apparently not reproducible reliably, but still: about the same response time as the Tomcat with no database activity and on a faster server. I also checked a different rails project of mine running on an equivalent VPS. Pages where two simple database request are involved, which, when directly invoked in psql, take 15 ms, take 300-400 ms to load if not cached.